Poultry Farm And Viruses

If you ask poultry producers what damage viruses can do to their business, they will think mostly about major diseases such as Avian Influenza, Gumboro disease or respiratory infections such as Infectious Bronchitis virus.

However, this is merely the tip of the iceberg. Viral challenges can be the triggers for a whole range of problems which may never even appear as clinical disease but can have an even more devastating effect on overall flock performance, production and profits.

Disease Factors

Poultry disease can affect one or more of the bird’s body systems, the most significant are :

Respiratory tract (lungs and air sacs) Skeletal system (bones and joints) Intestinal tract (affecting gut function). Although other factors such as environment, nutrition and management play an important role in the full expression of diseases affecting these systems, the most significant underlying trigger is usually an infectious agent, and the most potent of these are undoubtedly viruses.

Viruses do their damage by causing primary tissue damage or by opening the gates for other infectious agents, such as bacteria and Mycoplasmas, which might also be present just waiting for a chance to act. And if that wasn’t enough, a number of avian viruses can take this insidious yet highly damaging effect up to another level by directly attacking the birds’ immune system. This can cause clinical problems in its own right or prevent the bird from recognising other harmful agents. It can also prevent birds from responding to the increasing number of vaccinations given to a range of birds.

So why are viruses potentially more important than bacteria and other infectious agents? The first is their frequency. Common things are common. Poultry species can be exposed to a wide variety of viruses, even on high health status farms. Viruses can persist in the farm environment and diagnostic tests can be laborious, expensive and may make detection difficult. The next important factor is their impact. Primary viral infections can open the way for other secondary bacterial infections to cause ongoing chronic and severe performance losses Finally, all these aspects make viruses difficult to control.

Being subclinical and undetected, they can spread easily. They are not treatable with antibiotics. Viruses can therefore build up on farms especially if they are multi age and this can put too large a burden on vaccines which are considered by some to be the only effective defence against viruses. However, these vaccines can only work to their full potential if the majority of birds in a flock have an immune system that can respond to the vaccine and produce a robust and long lasting immunity.